6 Free Browser Tools That Fix KDP's Most Annoying Problems (No Signup)

Updated: 2026-08-26 · 7 free tools · all in your browser

I publish books on Amazon KDP, and the same small problems kept eating my time: guessing royalty numbers, converting ISBN-13 that Amazon pastes back into ISBN-10, formatting descriptions that get flattened on publish, and fighting the 50-character keyword limit — slot by slot, browser tab by browser tab.

So I built free tools to fix each one. They're 100% static HTML + vanilla JS — nothing runs on a server, nothing is uploaded, no account, no watermark, no "premium" upsell to unlock a basic feature. Open a page and it just works.

Here's the full tour, including the math behind them so you can trust the numbers.

🧮 1. KDP Royalty Calculator

→ https://aiharryone.github.io/kdp-launch-kit/royalty-calculator.html

The royalty formula looks simple until you hit a paperback with a $7.99 price.

The calculator handles the cases Amazon's own calculator makes you figure out by hand:

• Ebook (70% plan): royalty = 70% × price − delivery fee, where delivery is $0.06 × file size in MB, rounded down to $0.01. So a $4.99 book at 3 MB = $3.04.
• Ebook (35% plan): 35% × price, no delivery fee — useful when your price is under $2.99.
• Paperback & hardcover: 60% × price − printing cost, with printing cost from the book block size (page count + paper type). 250 pages, B&W, 6×9, $14.99 → $4.99 after printing cost.
• Breakeven price: the minimum price where you don't lose money per sale.

Pick your format, drag the sliders, see what you actually take home per sale and at 50 / 100 / 500 sales. Before I built this I was pricing paperbacks blind.

🔢 2. ISBN Converter & Validator

→ https://aiharryone.github.io/kdp-launch-kit/isbn-converter.html

Amazon hands you ISBN-13 everywhere, but some tools and KDP sections want ISBN-10, and mixing them up gets a listing rejected.

• Converts ISBN-10 ↔ ISBN-13 instantly.
• Validates the check digit on both formats — catches typos before Amazon does.
• Real check: 9780306406157 ↔ 0306406152 both validate and convert correctly.

Paste, convert, done. One less copy-paste-through-excel moment.

✍️ 3. KDP Description HTML Formatter

→ https://aiharryone.github.io/kdp-launch-kit/description-html-formatter.html

KDP descriptions support a tiny subset of HTML: <b>, <i>, <br>, lists. Paste a plain-text blob and Amazon flattens it — your carefully written hook becomes one gray wall of text.

This tool converts plain text into Amazon-ready HTML:

• Bold the key phrases, italicize what needs it
• Turn lines into a clean list with bullets
• Live preview on the right so you see exactly how it renders before copying
• Copy the result, paste into the description box

A conversion-focused description with formatted bullets converts noticeably better than a plain wall of text.

🔤 4. Keyword Character Checker

→ https://aiharryone.github.io/kdp-launch-kit/keyword-character-checker.html

Seven keyword slots. 50 characters each. Amazon truncates at 50 and silently drops the overflow — so your best keyword phrase gets cut off and you never see the warning.

This tool:

• Counts every slot as you type, showing characters remaining
• Flags any slot over 50 in red
• Saves your keywords in localStorage — close the tab, come back later, they're still there
• Lets you refine phrases to fit within the limit before you paste into KDP

The 50-character limit is per slot, and this is the tool I reach for on every single listing.

📐 5. KDP Cover Size Calculator

→ https://aiharryone.github.io/kdp-launch-kit/kdp-cover-calculator.html

Getting cover dimensions wrong means the whole KDP upload gets rejected — and the paperback cover math (front + spine + back, with bleed) is the one everyone gets wrong.

• Kindle ebook: exact 1600×2560, 1.6:1 ratio
• Paperback full wrap: front + spine + back with 0.125" bleed, 300 DPI
• Spine width formula from page count + paper type: white paper ≈ 0.002252"/page, cream ≈ 0.0025"/page. Verified: 250 pages, 6×9 → spine 0.563", full cover 3844×2775 px.
• Hardcover dimensions too

Enter pages, size, and paper — get the exact pixel dimensions to build your cover at.

⚡ 6. KDP Keyword Generator (Free)

→ https://aiharryone.github.io/kdp-launch-kit/kdp-keyword-generator.html

Staring at 7 empty keyword slots is the most common writer's block in publishing.

Give it your book topic and it returns all 7 slots filled with search-friendly keyword phrases — works for children's books, activity books, fiction, non-fiction. No signup, 3 free uses to try it out.

🚀 7. The Launch Kit Generator (The Paid One)

→ https://aiharryone.github.io/kdp-launch-kit/tool.html

The flagship tool, and the only one that isn't free forever:

1. Type one topic, e.g. "unicorn", "number tracing", "space exploration"
2. Pick your book type and audience
3. Get 5 ready-to-use title ideas, a subtitle, a conversion-focused Amazon description, and all 7 keywords — a complete, publish-ready listing from a single topic

3 free uses, no signup. After that it's a one-time $9.99 — no subscription, no per-book fee, no "unlock per listing" nonsense.

Why pay at all? Because the difference between a strong listing and a weak one is title + description + keywords — and this generates all three together in under a minute. It pays for itself on the first book.

Why These Exist (and why they're free)

KDP tools are a weird market: most "free" calculators are ads wearing a UI, gated features behind a 7-day trial, or upload your manuscript to a server and hope. I wanted the opposite:

• Static HTML + vanilla JS — everything runs locally, your data never leaves the device
• No signup, no tracking, no watermark — the free tools are free, forever
• Formulas verified against real KDP examples — royalty and cover math match Amazon's published numbers

If you publish on KDP and you're wasting time on listing math, one of these will probably save you an hour this week.

Try them free → https://aiharryone.github.io/kdp-launch-kit/

I'd genuinely love to know which tool helps you most — drop it in the comments.